What's Next for Solar Energy? How About Space

Scientists are closer than ever to making the far-out concept of a space-based solar collection system a reality

Think about what you know about clean sources of energy. What’s the greenest?

Hydroelectric, geothermal, wind and solar all probably spring to mind. Environmentally friendly though they may be, they all have significant limits on how much energy they can produce and where they can be used. To wit, despite some really cool advances in solar, solar panels still can only generate energy while the sun shines.

The solution, then, is obvious. Go where the sun never sets: in space.

That’s the vision of scientists, researchers and entrepreneurs both here in the United States as well as in Japan, China and Europe. Though the concept has been batted around at least since the 1970s, it’s been repeatedly revisited and abandoned because getting all the parts up there, and the people to put it all together, was impossibly expensive. Only with the advent of super small, mass-produced satellites and reusable booster rockets are some beginning to take a much harder look at making space solar a reality.
There are dozens upon dozens of ideas for how to build a space-based solar collection system, but the basic gist goes something like this: launch and robotically assemble several hundred or thousand identically sized modules in geosynchronous orbit. One part comprises mirrors to reflect and concentrate sunlight onto solar panels that convert the energy into electricity. Converters turn that electricity into low-intensity microwaves that are beamed to large, circular receivers on the ground. Those antennae re-convert the microwaves back into electricity, which can be fed into the existing grid.

John Mankins, who spent 25 years at NASA and Caltech’s Jet Propulsion Laboratory, received funding from NASA’s Institute of Advanced Concepts in 2011 to refine his space solar power plant concept in greater detail. The technology and engineering required to make space solar a reality already exists, he insists, but as with any expensive new idea, it comes down to greenbacks and gumption.

“It’s not like fusion—there’s no new physics involved,” Mankins says, referencing ITER, the 35-nation collaboration to build a fusion reactor in France. “There’s no secret sauce. It’s a financial hurdle to get funding to develop the elements and demonstrate the new architecture required to do this.”

Mankins and others estimate the total cost for developing, building, launching and assembling all the components of a space-based solar power plant is on the order of $4 to $5 billion—a fraction of the $28 billion price tag on China’s Three Gorges Dam. Mankins estimates a working scale model with full-sized components could be had for $100 million. By comparison, the Tennessee Valley Authority’s recently completed Watts Bar nuclear plant took 43 years to build, from start to stuttering finish, and cost $4.7 billion all told.

Critically, what consumers would pay—the price per kilowatt-hour—needs to be in the same ballpark as conventional sources of energy produced with coal, natural gas and nuclear, which range in price from 3 to 12 cents per kilowatt-hour. Hydroelectric can be staggeringly cheap, at less than one cent per kilowatt-hour—but only if you’re lucky enough to live in a region with abundant high-flow rivers, like in parts of Canada and Wisconsin. Geothermal is very economical too, checking in at 3 cents per kilowatt-hour, but you’ll need to ask the Icelanders how they like their power bills. And wind advocates trumpeted the news last year that costs for that renewable resource had plummeted to 2.5 cents per kilowatt-hour.

Getting the cost into the low double digits or even single digits of cents per kilowatt-hour is absolutely essential to make space solar a competitive utility, says Gary Spirnak, CEO of the California-based energy company Solaren.